Devices for modulating electromagnetic radiation represent fundamental building blocks for many technological endeavors. Modulation refers to the variation of a property in an electromagnetic wave or signal, such as amplitude, frequency, phase, spectral content, or any other measurable characteristic. In addition to dynamic modulation processes that are operable in real time relative to a period of the radiation, modulation further refers to the tuning or adjustment, whether it be static or dynamic, of a system or device that varies any such measurable characteristic of the radiation.
For frequencies in the microwave range, modulation is often achieved in solid state devices by variation of inputs and/or operating parameters for electrical components such as heterojunction bipolar transistors, metal-semiconductor field effect transistors, and Gunn diodes, and/or in vacuum tube based devices such as magnetrons, klystrons, and traveling wave tubes, in each case in conjunction with associated passive electrical components. For optical frequencies, modulation is often achieved using devices based on electrooptic and/or magnetooptic materials such as calcite, quartz, and lithium niobate that change their refractive index responsive to applied control signals, the materials being arranged into Mach-Zehnder interferometers (MZIs) or similar devices converting induced phase changes into amplitude changes by interference effects. Other electrooptical modulators include electroabsorption modulators variably absorbing the incident signal according to an applied electric field, and acoustic wave modulators using high-frequency sound traveling within a crystal or a planar wave guide to deflect light from one place to another.
For each of the above schemes, practical issues arise in regard to one or more of modulation speed, dynamic range, spectral range of operation, noise performance, channel selectivity, device cost, heat dissipation, device size, tunability, and device power consumption. It would be desirable to increase the number of device solutions available for any particular radiation modulation requirement, and/or to provide for improved radiation modulation with respect to one or more of the above practical issues. Other issues arise as would be apparent to one skilled in the art in view of the present disclosure.